The present invention relates to mounts for proximity sensors and more specially though not exclusively to such a mount having a cylindrical housing with a male thread on its outer face.
Proximity sensors are used to detect the position of one part in relation to another part without making physical contact. For example, use may be made of electromagnetic sensors in the form of inductive or capacitive proximity switches, that respond to metal members near the detection element of the sensor. For such proximity switches, the design may be in the form of a cylinder, see for example the Standard 50008 D.
For mounting a proximity sensor and for adjustment of its switching point, the sensor is normally screwed into a suitable threaded hole. Its adjustment in the axial direction is undertaken exclusively by a screwing motion. When the final or desired position of the proximity sensor has been reached, in which it gives the desired switching function, the proximity sensor is locked in place by a lock nut on its outer screw thread.
This way of mounting a proximity sensor has a number of shortcomings. The axial displacement using a screw thread is admittedly very suitable when it comes to producing the desired fine adjustment of the sensor, but however there is no way of producing a coarse adjustment quickly. Frequently, the proximity sensor has to be revolved a large number of times before it is in its desired position so that the fitting operation becomes involved, tedious and time-consuming. Furthermore the locking of the proximity sensor in place with the lock nut is apt to be problematical. Such a nut only acts on a very small part of the circumference in relation to the axial length of the proximity sensor so that the resulting gripping forces act more or less at one small point or range and this is likely to cause a local deformation of the proximity sensor. This may lead to trouble conditions, which may make themselves felt in anything ranging from a misalinement of the switching point to complete failure of the proximity sensor. A further point is that on fixing a proximity sensor in place careful attention must always be paid to not exceeding the permissible torque for tightening up the lock nut to make certain that the detector elements are not damaged. The direct mounting of a cylindrical proximity sensor in a threaded hole is therefore frequently more troublesome than one would expect at first sight.